Full Games

This list contains free full games that you can install and play on Steam. You do not need to own any other games and there are no string attached. You only need to download and install Steam (free) if you haven't already installed it.

Full Game Mods Based on Source Engine

"[These games require] that you own a Source engine game such as Counter-Strike: Source, Half-Life 2, or Day of Defeat: Source. Click here for a full list of games that meet this requirement. Please note that Portal: First Slice and the bundled Half-Life 2: Deathmatch do not fulfill this requirement." - Steam Store